Juniper MX2020 Hardware Manual page 85

CPU—Runs Junos OS as a guest OS to maintain the router's routing tables and routing protocols.
I2C bus logic, used for low-level communication with each component.
DRAM—Provides storage for the routing and forwarding tables and for other Routing Engine processes.
Component redundancy circuitry.
USB ports—Provides a removable media interface through which you can install Junos OS and Linux
manually. Junos OS supports USB versions, 3.0, 2.0, and 1.1.
Solid-state drives (nonremovable)—Provides secondary storage for log files, memory dumps, and system
reboot.
Interface ports—The AUX, CONSOLE, and MGMT ports provide access to management devices. Each
CB-RE has one 10/100/1000-Mbps Ethernet port for connecting to a management network, and two
asynchronous serial ports—one for connecting to a console and one for connecting to a modem or other
auxiliary device. The two SFP+ ports (XGE-0 and XGE-1) provide support for hardware diagnostics and
JCS port testing. The EXTCLK1 and EXTCLK2 ports provide access to external timing distribution.
NOTE: Use sheilded CAT5e cable for connecting the AUX, CONSOLE, and MGMT ports.
EEPROM in RE—Stores the field replacement unit (FRU) details of the RE.
EEPROM in CB—Stores the field replacement unit (FRU) details of the CB.
RESET button—Reboots the Routing Engine on the CB-RE when pressed.
ONLINE/OFFLINE button—Makes the Routing Engine on the CB-RE online or offline when pressed.
NOTE: The ONLINE/OFFLINE button must be pressed for a minimum 4 seconds for the
power off or power on to occur.
LEDs—Provide status of the Routing Engine on the CB-RE.
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